As a conventional color image formation apparatus, for example, tandem type apparatuses are well known. The tandem type apparatus has a configuration in which a plurality of optical scanning apparatuses are provided on a paper feeding path placed in a manner in which it extends horizontally, and toner images are transferred from the respective optical scanning apparatuses sequentially to a paper that moves along the paper feeding path, thus forming a color image on the paper.
As the optical scanning apparatuses used for the tandem type color image formation apparatus, an apparatus merely using four conventional optical scanning apparatuses each scanning a single flux (see JP2000-141759A), an apparatus using a single optical deflection unit and four sets of lens systems (see JP2001-133717A), and an apparatus using a single optical deflection unit and four sets of curved surface mirrors and lenses (see JP10 (1998)-148777A) are well known.
However, any of the above-mentioned conventional optical scanning apparatuses have a problem that a large number of components are required, so that miniaturization of the apparatus is difficult and the cost becomes high. Furthermore, since a plurality of lens systems are used, it is difficult to provide uniform performance of respective scanning lines.